If there is one thing that slows me down its the way the 901 tranny and its associated linkages shift.

What are all the tricks to making the linkages better for a race car? Is there good aftermarket shifters, linkages etc that make things a little more positive?

- there are better shifters out there
(rennshift, wevo, ajrs)
- straightened shift rods
- custom firewall bushing
- custom shiftrod knuckle
- custom rear shift console bushing
- custom rear shift cup (for cup bushing)
- custom motor and tranny mounts.

brant

Brant,

I have been thinking about a two piece shifter cup for the rear shift console made from stronger material than the soft plastic.

What are your thoughts on this?

Something that is actually held together by the shift coupler as it slides over it??

If you look at ErikM's Hewland/MK box, it has a steel ball in a steel socket. I would like to mimic this in some form or fashion.

The other thing we do Grant: extend the shift rod and support it in another bushing at the back side of the console. This is VERY similar to what Hewland does in their boxes.


B

Not to wander too far off the path, but I've been thinking about this, too.

That whole ball slider in a cup thing is wacked. It's taking fore-aft motion and making it rotate the shifter in the trans. There's got to be a better way.

It's got me thinking I'd be better off with a 901 from a 911 from a shifter stand-point...

Kevin,

The actual motion inside of the 901/914 tailshifter is better than the ball/cup shift console. The main issue with it is how the shift rod engages the shaft hanging out the box.

You are correct. You could easily do a Monkey Motion like the Hewland on the back of a 901/911 box (cause the 901 is very very similar to the Hewland VW boxes)..it says VW on the case for gods sake!!..lol


B

I stole erics picture for over here..
I think thats a very interesting idea Brad.
it wouldn't be that hard to try it.

my cup is modified but still uses the stock plastic slider bushing.
at full range of motion, the bushing is pulled about 1/8 of an inch beyond the edge of the stock metal cup.

so my cup has been extended
the extension is welded on and then the inside is re-machined and honed to make it seamless on the inside sliding surface.

this provides a tiny bit more rigidity during full range of motion.

but I like the metal ball idea.

brant

ooops...

Why not just learn how to shift the damn car.
seriously Snug up the bushings and adjust the shifter.

I don't have a problem shifting my car. however other 914's I have driven are a bit wierd.
Some I agree are like shifting with a bowl of chocolate pudding for the connection.

Joe, PLLLLEEEEEEAAAASSSSEEEEEE. They suck, We all can do it, but why should we.

These cars can be made to shift very well.

Heres what I have done recently and am VERY happy.

RENNSHIFT. The best I have tried, I know Brad is partial to another, but I really like this one.

Side shift only:

Measure the tab on the front of the console and then the distance for the hole from the plate. Fabricate a tab to be welded to the rear of the console.

Mill some .380 plate so that it is the same. Don't drill the hole yet. Basically you have made a tab that is the same as the front tab. Weld the tab to the rear section of the shift console after removing it from the transmission of course.
Then drill the second hole in the back tab that you welded on. You may have to choose a drill size that will clean up the front hole by making it just a touch larger.
Now you will have a shift console that will have two holes in it so that a rod will slide fore and aft in the same plane.

You will need a machinist to spin up another shift rod (the piece that the shift knuckle attaches to) it should be much longer now because it will now pass throught the rear tab that you fabricated, The front part of this rod which is a straight piece that is larger (.580). Most of the shift rods I have seen are hammered and if you run them in delrin, the bushings will get wooped quickly. What you are making is ONLY the straight part of the shift rod, not the curved part.

Build two delrin bushings for the shift console tabs. Be carefull the fore and aft motion is critical, and the forward motion is very close to the front tab so make sure the bushing shoulder on the inside of shifter console is fairly thin. This is one of the areas you will eliminate a ton of slop. Not to mention changing the way the shift action at the transmission works.

You will now need a 5/8 APEX joint. Weld the apex over the top (be sure to use the cooling paste they sell it really works) of the large step of your straight shaft. Now you will need to assemble everything and mark the shaft you made so that you have enough fore and aft throw. The rotational angles are really not important at this point. Mark it and you will have to drill it for the set screw. i think I used a #30 drill bit and a tapered reamer until I got the desired angle and depth.

Next, You should now have a straight shaft that is supported at the back and the front of the shift console, assembled on the transmission, and the shift knuckle and shaft held in position by the original set screw, with the bushings installed and held in place by a washer and circlip.

Now you need to connect your original shift shaft to the apex joint. I like to machine a small slug that welds to the apex joint and is "fittted" (ie... cut and weld) to the original shift shaft. Once you have centered the shift shaft and welded it. Paint it. Adjust it inside the car.

Enjoy it. When i did it, I could not believe how good it was.

If you want to, you can also add an APEX joint to the front coupler. I did not but you could.

I would take some photos, but the car is nowhere near me.

The difference is amazing. The gates are where they are supposed to be everytime. it works good. Hope this is clear enough.

Erik

Damn,

did you have some free time tonight?? LOL The only thing missing from your post was the engineering blueprints

All jokes aside, thanks for the writeup. The person Grant uses to maintain his 914 will understand what we are talking about. I'm trying to locate a pic of a shift console so I can photo edit what we are talking about.



B

Here we go.. this should make it a little more clear for those of you scratching your head about adding a second support and extending the shaft.

We are also talking about making/replacing the white plastic piece with a metal two piece unit.


B

Now thats What I am talking about.

Except for the plastic bushings. Since the shift rod will rotate and slide in the same plane, the clearances can be much tighter. But what Brad has photo shopped is the exact thing I have built. Works very well.

Erik

Replace it with a better tranny.

Can't think of anything else.

Brett,

I think you missed his original question

He didnt ask if there was a BETTER tranny (duh! of course there is)

He asked if we could make a 901 shift better. (duh! of course you can!)


B

Actually here is something that Brumos does on their cars.

There you go! That is actually what I'm talking about. Good shot of it. If you had been around earlier.. I wouldnt have had to exercise my photochop lack of skilz!!


B

I played "admin" and cropped/resized it for you


B

For some reason I was just being an ass.

Leave that to me! I'm better suited and more well known for being an asshole!!

Watch this:

Grant,

I think you should build a big type 4 for your car..LOL


B

Better yet, I think you should let Jake build it.

Very clever!!!

One question. The Apex joint is applied just before the shifter console, no? It seems like that's where it belongs.

If you and Erik get this organized and make the pieces Brad, please figure out what it would take to make another. Urgently needed as you know and understand.

Correct Kevin!! install the apex joint just in front of the shift console.

Randal,

this may be something I can get done quickly. I have just about everything needed to complete one.

Let me see what I can do.


B

I will have a linkage kit that does all the things you guys are talking about - it is in production and will be available in about 60 days.

This is not vaporware - I designed it about a year ago but it took a while to make it a marketable product. To me, that means fully sealed with rubber boots and adaptable to different configurations while being as affordable as I could make it.

I have a machined support with bronze bushings that supports the shift rod on both sides of the shift head inside the console. Included is a rear shift rod section and u-joint and boots to keep the whole thing sealed.

At the firewall, I have an appliance that mounts a spherical bearing and a new shift rod section with a u-joint. A rubber boot protects the bearing.

Replacement of the ball cup is not needed - new plastic is fine. I created and used a new lever at the transmission with a spherical bearing mounted in a bronze sleeve to replace the cup bushing. The difference was too small to be perceived. I also evaluated it in a 911 at the base of the shifter with similar results - it was not worth the effort.

Show us

Erik said something about me and Rennshift..

Erik,

I have pushed/sold more Rennshifts than WEVO shifters. WEVO doesnt have a 901 solution because of James' products. I was working with them on providing a solution when James hit the market with his setup. The market segment was too small for them after running the sales numbers.

I have a car right now we can test on. We have 2 more events before the end of the year.


B

Oh, I will - the testing is done and the money has been spent - so I have to now!

No spy shots, though - there will be a grand unveiling when they are ready to ship.

James,

Will your new linkage kit be compatible with the RennShift? I assume it would be. I am curious since I just purchased a RennShift.

This has been an interesting thread.

Yes, it can be used with the stock or RennShift side-shift shifter.

James,
Do you have an approx. price for the linkage kit?

GB

I will separate the firewall and shift console parts into two separate kits at around $200 each. There may be a slight discount when you buy both at a ballpark of $400.

There is finish work required, but it is low precision - non-critical fitment.

I will supply loose splined ends for the u-joints to make to your own tube to connect the two kits together. Because the u-joints allow 360 degree clocking, it will be easy to fabricate - basically just get any clearance bends in (such as needed for a 4 cyl) and make the length right and have the new ends welded to a tube. You can correct for rotation later with the u-joint connections and alignment is not critical because there are u-joints on both ends.

The firewall kit will also require re-use of the solid splined portion of the factory shift rod up by the shifter - just grinding off the welds and tacking it to the new tube I supply. This part does not wear out so I see no need to reproduce it.

I may offer the kit fully finished later, but to start I want to keep the price down and keep it simple.

Just my .02, but....
When the internals of your tranny are trashed, none of this stuff will help you.
If your tranny is trashed to the point where a gear or 2 are missing from the party, it has probably been fucked up for some time and you have no idea how a properly functioning 901 should work. If the trans has been trashed under your ownership, it might also be a good idea to replace the wear parts in the linkage....since you're there.

IF you have a fresh, properly built up trans....I'm talking a guru built unit, no filed sliders/dogteeth, bearings that "look OK"...new stuff..only then can you judge for yourself whether or not these goodies are worth their cost or just taking up the space of your old parts. No sense putting the cart ahead of the horse, eh?

This post has been designed to offend as many people as possible

Ha ha...

People FREAK out when I tell them 5k to rebuild a tranny. They typically have a WTF? look on their face..LOL

I tell them: you spent 10k rebuilding your engine.. 5k on paint.. and 5k on the tranny "bothers" you?? WTF?? LOL


B

What can be done to the inside of the transmission? I have heard that removing everyother tooth on the syncro hub and the selector ring would help it to engage quicker. I thought about trying this in my ITC car.

Correct. Linkage and shifters help to find the right gear at the right time without concentrating as hard (and if you think you have some extra concentration to give up you are a better driver than most pros).

The actual gear engagement is dependant upon good trans internals - no way around that!

Whaoo, crash box
Back in the day, we'd take a t-10 4 speed and remove 2 of 3 dog teeth off the gear and likewise off the slider, IIRC....hay, it was 40 years ago. The brass syncro rings could be bought with no dog teeth.
......the Borg Warner syncro set up is a bit different that the Porsche syncro....better, I might add. Porsche went to it with the G50.
Anyhew, it would shift like lightening....going up. I tried to downshift it one time....but never again. An rpm matched double clutch prolly woulda worked....but drag racers don't bother with that stuff.

Agreed. However I'm focused on linkages with this post and making assumption that 901 internals are working properly. I have plenty of expereince with good 901's to say shift linkages could use some help in making shifting more intuitive.

I know you come from an era of driving turn of the century tractors and think a "modern" 1960's design synchromesh tranmission and associated linkages are state of the art. Some of us youngsters just dont have an appreciation for the art of finding the right gear like you do JP. Didnt you learn to shift on one of these back in the day?

Nah, for those I drove you had to stoke the boiler with wood. Shifting was via the Johnson bar......

Thank you Thomas

Jared,

I know of 5 tranny builders in the USA who actually "rebuild" 901/914 tranny's. The rest of them replace worn parts with more used parts.

Very few people know what a 901 feels like with all new parts.


B